1. Field of the Invention
The present invention is directed to uninterruptible power supplies and more particularly to an inverter for supplying an alternating current to a load from a storage source of direct current.
2. Description of the Prior Art
In today's wide use of computers, data processors, controllers, etc. in data processing systems, it is extremely critical that the system be supplied with continuous power during its operation. Due to inadequate capacity and increasing load demands, commercially-supplied power is often subject to complete failure of the power signals or a reduction in the magnitude of the available voltage during peak demand periods. In cases where various customers subject the power system to sudden electrical loads, transients are generated in the system affecting the magnitude and phase of the supplied power signal.
Since the storage of data in a computer system is predicated on the continuous operation of the computer, power interruptions can adversely affect the integrity of the stored data. When the power drops abruptly, the computer will terminate operation probably with a high possibility of component damage. In order to overcome this situation, computers operating in a data processing system environment have been supplied with uninterruptible power supplies. Such uninterruptible power supplies have been designed where the primary commercial power source and the reserve power source are connected in parallel. Both the primary power source and the reserve power source are continuously operated and both sources contribute to the energizing of the load.
In a prior uninterruptible power supply arrangement, the power supply includes a commercial A.C. line power source and a D.C. voltage energized inverter power source connected in parallel to a switching mechanism which alternately couples one or the other of the two power supplies to a load to be energized. It is desirable that the auxiliary power source comprising the inverter be switched into the A.C. power line at the time the A.C. line power source fails. Prior inverters using controlled rectifiers or other types of switching members require switching to occur at the zero crossing point of the line signal.
It is therefore a principal object of this invention to provide a D.C. to A.C. inverter for generating A.C. power signals from a D.C. source at the time of power failure of the A.C. line source.
It is another object of this invention to provide an inverter using semiconductor field-effect transistors (MOSFET) for switching the output of a D.C. source at a high frequency rate which is synchronized with the line frequency.
It is a further object of this invention to provide an inverter which is simple in construction and low in cost.